The director Annie Castledine's idea of perfect happiness is to be moved to tears in the theatre. So directing Euripides' savage and desperate tragedy Women of Troy has her basking in bliss. It's a weep a minute; a terrible, tense tale of the women who have survived the sacking of Troy only to get carted off to slavery. "It's not only a play's content or the expression of huge emotion that moves me," she says. "It can be an image arriving out of nowhere or the sheer exhilaration of seeing great performance skills - a performer reaching a top A."

Castledine is once again collaborating with Annabel Arden, a founder of Theatre de Complicite. Big women bundled in woolies and bursting with passion and enthusiasm, they make a formidable team. "We share fags and a love of the Greeks," Castledine explains. "I've known the Greek plays and myths since I was five. These characters - the heroes, the gods, the mortals - are as familiar to me as my intimate family, part of the imaginative hinterland, the reservoir into which I dip." While others had Elvis pinned on their bedroom walls, the young Castledine only had eyes for Hector, the greatest of all the Trojan warriors. "As a child, Hector peopled - personed - my room. He's been there and I've spoken to him. Several times." She says this with a deadpan matter-of-factness that elicits a giggle but defies contradiction.

Arden's immersion was similarly early, intense and intimate, but for her the delight of the play is that "it makes you think as well as get emotionally involved. In the theatre - or anywhere else at the moment - there's very little dialogue or debate, no one really thrashing it out. We need plays like this to get us talking. "

A buzz of a less elevated sort began weeks ago when Jane Birkin (Serge Gainsbourg's muse who sang to notoriety with "Je t'aime" in the Sixties) was announced as top of the bill. (Euripides' great arias of verse are tough for a seasoned Shakespearian, so for a film star with a French accent making her British stage debut, the challenge is immense.) Castledine, who, staggeringly, had never heard of Birkin or "Je t'aime", says she saw in her precisely the quality she wanted for Andromache. Three years ago Birkin's lover and father died in the space of a week. "Her pain was so tangible, it was like her skin was only barely holding her in. She is so unaffected, so herself. A strange liaison, me and Jane, but there we are. She is so pure, like a gentle pained dove. Wonderful physically. Vocally? We'll see."

Last week, Castledine's Hecuba also caused a stir. Rosemary Harris, nominated for an Oscar for Tom & Viv, has not been given permission to bunk off and attend the awards ceremony. Castledine and Harris remain devoted to one another, nevertheless. They have worked together before, most recently on Arsenic and Old Lace. "If you've had a thrilling creative journey with someone, you want to pick up where you've left off. I was casting Hecuba from a position of frailty and female beauty as opposed to huge strength. The strength has to be found through the vulnerability. I also wanted a performer who could be at home with the concept of being a queen, and a rather rich queen, without us ever having to talk about it. There are certain things that you want to be acted qualities and certain things you want to be natural qualities. Rosemary Harris has a natural grace; she has to find that deep reservoir of grief, that understanding of pain in the depths of her imagination," explains Castledine, her reply building into a speech of roundly annunciated, emphatic statements - a reminder that she was once a teacher, and doubtless a visionary one.

The four lead actors could scarcely be more sharply contrasting. Josette Bushell-Mingo plays Cassandra ("I always want to work with her, in every single piece of work that I do, but I have to ration myself. A director can do anything or go anywhere with such a performer.") And Janie Dee, best known for singing and dancing up a storm in Carousel, plays perhaps the hardest role of all, Helen of Troy, the Marilyn Monroe of myth. "I fell in love with Janie at the audition," Castledine says. "And I thought, this person will well be able to encompass Helen of Troy, a woman who is desire. She is the personification of desire and she inspires desire, that flame of desire that possesses a being so that every rational thought is abandoned."

Castledine calls Women of Troy the ultimate anti-war play. "Euripides is saying that there is an integrity to war, but the emphasis and condemnation lies in the fact that there has been extraordinary slaughter over and beyond the conquest of a people. Our priority then and now is to extend our hands across cultural barriers to grasp our common humanity. If we ignore that, we are condemning the whole human race; I think that's what Euripides thought."

To help the cast make connections between Euripides' concerns and contemporary warfare she showed them footage of forced movements of people, the diaspora, the situation in the Balkan states, the Kurds, Iraq, Iran. Arden, meanwhile, began work on what she calls the "physical text". "I'm concerned with the quality of presence and stillness on stage. What we want is heightened naturalism. It's not choreography, not mime, not gestural. It explores how you express shame or pain or grief without resorting to the sort of thing you see on television where people contort their face in agony. I'm interested in the qualities that a great piece of either figurative or abstract sculpture can project; it's all to do with angle and mass and tension." As Castledine says, they are at pains to avoid "a splurging generalised emotionality. These characters aren't indulging in self-pity, they are probing how it is that this terrible thing has happened."

Castledine confesses that it's the hardest thing she's done, but also the most sublime. "When you spend so many weeks in the presence of a great playwright with a challenging voice and a political consciousness, then your quality of life goes into the stratosphere. The choices you make are much more important." One choice was not to use masks, preferring a less stylised approach, but to use veils instead. "A veil is a mask analogy. Veils are sometimes seen as a symbol of oppression but they are actually about power. In this play the disempowered women have language and their veils, which they can use to obliterate their features from those they don't want to look at them." It was an idea she had while walking down London's Edgware Road. "I saw two women and was struck by their friendship, yet one was very Westernised - not veiled - and one wasn't. One was making a statement about not wanting to be looked at in a Western way, but there was no conflict."

It is inventive touches such as this which have won her praise in the past for making classical theatre "accessible and appealing". But she claims that she never considers the age or status of a play. "The curse of our theatre is the linear, suburban imagination which has to be literal about time and place. These characters - us in extraordinary mould - speak for us in those two hours that we are sharing the act of theatre; we should say, `yes' we have thought that, `yes' we have felt that, `yes' we would like to scream like that; in doing it for us, the characters allow us to also experience the scream. Hugely cathartic, hugely important. Classless, timeless, placeless. "